This new text provides a fresh approach to the subject of animal physiology, truly integrating comparative and environmental aspects for the first time. The book is divided into three sections: the first covers the basic principles of adaptation and problems of size and scale; the second tackles the key mechanisms in comparative physiology; and the third considers in detail how organisms (both vertebrate and invertebrate) cope with particular environments. Throughout this final section, relevant comparative aspects are given prominence in boxes so that interesting topics can be explored in greater depth. Several textbooks deal with the physiological functioning and comparative adaptations of animals, but this one is different: Includes both comparative systems physiology (basic principles and mechanisms of excretion, thermal biology, respiration, etc) and environmental physiology (problems of life in different habitats), with easy cross-reference between the two. Analyses and integrates problems and adaptations for each kind of environment: marine, seashore and estuary, freshwater, terrestrial and parasitic. For example, it explains how seashore animals survive both tidal submersion in cold salt water and exposure to warm dry air, cope with wide variations in salinity and temperature and achieve both aerial and underwater breathing. Examines mechanisms and responses beyond physiology. It analyses the costs of different types of locomotion, together with the mechanical challenges and varying sensory needs imposed by different environments. Behavioural responses to environmental challenges are considered, including the evolution of mating systems and life-history strategies, as well as responses to stresses imposed by humans. The book therefore integrates the biochemical, physiological, behavioral and ecological adaptations that allow animals to survive in particular environments. Applies an evolutionary perspective to the analysis of environmental adaptation. It introduces modern, phylogeny-based comparative methods that have become standard techniques in the analysis of evolutionary patterns. Provides modern molecular biological insights into the mechanistic basis of adaptation, and takes the level of analysis beyond the cell to the membrane, enzyme and gene. Incorporates more varied material from a wide range of animal types, with less of a focus purely on terrestrial reptiles, birds and mammals and more on the spectacularly successful strategies of invertebrates. This is a core text for modern undergraduate courses in animal physiology, comparative physiology, environmental physiology and physiological ecology. It is also suitable for the physiological components of any animal biology course, and a key resource for degree courses in environmental biology.